This invention relates to styrenic tetrapolymers and specifically to a process for the production of such tetrapolymers.
The tetrapolymers of the invention are particularly useful in the production of a commercial ABS formulation with advantageous properties.
As is well known in the art an ABS polymer essentially comprises particles of a diene rubber substrate grafted with styrene and acrylonitrile dispersed in a matrix polymer comprising styrene and acrylonitrile. In one variation of such ABS-type polymers, part or all of the styrene is replaced by .alpha.-methyl styrene in the matrix polymer. This has the effect of raising the heat distortion temperature of the ABS by several degrees.
Unfortunately this technique has only a limited capacity for producing distortion temperature improvements in a commercially acceptable product. The present invention however indicates that ABS polymers with much better heat distortion characteristics can be obtained using a tetrapolymer prepared by the novel process herein described.